Stair wheeler

ABSTRACT

A suitcase having a telescoping pull handle and a set of spaced apart wheels, between the back panel and bottom wall of the suitcase housing, permits easy movement over a planar surface. A staggered wheel mechanism is pivotally mounted on the back panel of the suitcase for improved mobility of the suitcase over a flight of stairs.

CROSS-REFERENCE TO RELATED APPLICATIONS

Provisional Application Number: 60895741

Receipt Date Mar. 20, 2007

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

N/A

REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX

N/A

BACKGROUND OF THE INVENTION

The present invention relates to staggered wheel mechanism to facilitate transporting a traditional wheeled luggage e.g. suitcase over a flight of stairs. The staggered wheel arrangement offers a near linear, continuous, rotary outer surface when in contact with the edge of the steps thus greatly enhancing the mobility of the suitcase over a flight of stairs. The staggered wheel mechanism can also be used on a shopping basket or any other embodiment that requires easy and quick movement over a flight of stairs.

Traditionally, suitcases have been designed with a set of wheels at the bottom or bottom corners of the suitcase. Wheels permit the suitcase to be easily rolled across a planar surface even by an individual who would not normally be able to physically carry the suitcase from one location to the next. Whilst traditional wheeled luggage greatly enhances mobility over a planar surface an individual is faced with dilemma when they encounter a flight of stairs over which the suitcase has to be transported. Airport and some train/bus station or some other public places have escalators, elevators to facilitate luggage movement from one floor to the next and avoid stairs. However there are greater number of public places and residential places where there is no easy means to move the luggage between two different floors or even to negotiate a few steps.

Some traditional suitcases come with skids wherein the individual can slide the suitcase over each step. The skids mounted on the back panel of the suitcase rubs against the steps and since the skids are not frictionless it can damage the stairs if made of wood, carpeted or leave marks on the steps. In addition to the gravitational force the user will have to expend additional force to overcome the friction. Secondly when suitcase is pulled over steps in near upright position the back of the suitcase can slam against the stairs as it leaves contact with one step and engages with the next. The friction and jerky movement can lead to additional strain on the hand leading to injury and could also damage fragile articles within the luggage compartment. So a typical rolling suitcase is not well suited for moving luggage up and down a flight of stairs.

Prior art has been proposed that includes features designed to facilitate easier movement and alleviate the burden of transporting a piece of luggage over stairs. Such solutions are either not practical or have inherent drawbacks that the present invention overcomes

U.S. Pat. No. 5,575,361 to Chou discloses a wheeled suitcase. Chou's suitcase places the rollers on the bottom of the suitcase so the suitcase can be easily wheeled over a flat surface but has no means for towing the suitcase up a flight of stairs.

U.S. Pat. No. 6,041,900 to Sadow et al. discloses a towable article of luggage. Sadow's improvement places wheels not only on the bottom of the luggage but also on the front face of the luggage. Again such use of additional wheels does not permit towing the suitcase up a flight of stairs.

U.S. Pat. No. 6,938,740 to Cheryl Gandy discloses a suitcase with a stair roller and brake. Further the rollers are affixed directly to the back of the suitcase housing. In addition such rollers are mounted with or without endless circumscribed belt. Such a solution does make it easier to move a piece of luggage over the stairs in comparison to dragging it up on skids but has the following drawbacks;

1. If the embodiment uses only bare rollers:

-   -   A. The movement of the suitcase over the steps will be ratty         cause of the grooves between two rollers.     -   B. Depending on the size and spacing of the rollers the edge of         the steps may get lodged in the groove formed between adjacent         rollers.     -   C. Because of the grooves between two adjacent rollers a higher         initial force will be required to begin the accent and whenever         the user stops on the stairs. The article will have to be kept         in rapid motion over the flight of stairs to avoid using the         extra force.     -   D. The grooves will cause a higher wear of rollers and thereby         the life and reliability of such a roller arrangement will be         shorter. The reliability will be compounded by the weight of the         article.     -   E. The size and weight of the roller arrangement can reduce the         overall payload.     -   F. Since the rollers are affixed to the suitcase housing it will         slam against the steps, when pulled in an upright position, as         it leaves one step and engages with the next. This will further         worsen the wear and tear of the rollers.

2. If the embodiment uses rollers with endless belt;

-   -   A. The belt will have to be maintained at correct tension         throughout the life of the suitcase due to aging and normal wear         else the belt will start to develop some slack. This can lead to         dragging of the luggage over the steps instead of neatly         rotating over the steps.     -   B. The part of the endless belt between two wheels will be         subjected to pressure by the steps edge causing the belt to         loose tension over time.     -   C. The endless belt will thus need frequent replacements and         maintenance     -   D. The dimensions and weight of the such a roller arrangement         with circumscribed endless belt can reduce the overall payload     -   E. Again since the rollers are affixed to the suitcase housing         even with a circumscribed belt the slamming against the steps,         when pulled in an upright position, as it leaves one step and         engages with the next, now the belt will be subjected to a         greater wear and tear.

W.O. Pat. No. 2006/045107 to Michael Yang, Sadow et al. discloses a collapsible spider wheel assembly that could be used on a suitcase and could be used to move the luggage up the stairs but has drawbacks in that the movement will be slow and rattly. It is more suited to be used on handcarts to move heavy loads.

BRIEF SUMMARY OF THE INVENTION

The present invention overcomes the aforementioned problems and drawbacks of prior art and provide a mechanism that would make the embodiment highly maneuverable over a flight of stairs when ascending or descending.

An article of wheeled luggage having improved mobility characteristics employs a staggered wheel mechanism pivotally mounted on the back panel of the embodiment to easily move and transport it over a flight of stairs. The staggered wheel mechanism consists of two pluraly spaced wheel assemblies and a foldable link structure. Each wheel assembly in turn has two in-line wheel arrays arranged in a staggered fashion in the wheel frame. Such a staggered wheel arrangement creates a near linear, continuous rotary surface which will result in a smoother movement of the luggage article over the stairs. The staggered wheel mechanism can be stowed away in the recesses of the embodiment when not in use. The invention does not employ a braking mechanism since the embodiment can be simply straightened out on the steps to stop the suitcase in mid flight.

The strengths of the present invention will become readily apparent in the following detailed description and diagrams of one of the preferred embodiment. The preferred embodiment in this case is a suitcase.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings like reference numerals denote similar elements throughout the several views

FIG. 1: Perspective view of the preferred embodiment, suitcase, with staggered wheel mechanism fully deployed.

FIG. 2: Partial side view of the wheel assembly showing a near linear, continuous rotary outer wheel edge.

FIG. 3: Perspective view of the suitcase with retracted staggered wheel mechanism and extended telescopic handle.

FIG. 4: Perspective view of the suitcase with back panel recesses

FIG. 5: Perspective view of the towing apparatus that fits in the back panel recesses of the suitcase

FIG. 6: Perspective view of the staggered wheel mechanism partially deployed

FIG. 7: Perspective view of the retracted staggered wheel mechanism

FIG. 8: Simplified side view of the towing apparatus showing staggered wheel mechanism's linear outer wheel edge

FIG. 9: Partial perspective view showing a wheel frame's two channels and staggered arrangement of axles in the channels.

FIG. 10: Partial top view of the wheel frame

FIG. 11: Exploded perspective view of the staggered wheel mechanism

FIG. 12: Partial cross-sectional front view shows the pivotal connectivity between the upper link of the link apparatus and suitcase back panel bracket.

FIG. 13: Top perspective view of the link apparatus hinge and torsion spring

FIG. 14: Exploded perspective view of the wheel assembly

FIG. 15: Partial front view of top end of the wheel frame

FIG. 16: Perspective view of staggered wheel mechanism with protruding top wheels

FIG. 17: Side view of the embodiment on stairs

FIG. 18: Simplified partial cross-sectional side view of the sliding latch mechanism area

FIG. 19: Simplified perspective view of the sliding latch mechanism area

FIG. 20: Exploded perspective view of the sliding latch mechanism

FIG. 21: Partial perspective view of mounted pivotal latch mechanism

FIG. 22: Exploded perspective view of pivotal latch mechanism

FIG. 23: Exploded perspective view of the latch lever mechanism

FIG. 24: Perspective view of the staggered wheel mechanism embodied on a shopping cart

FIG. 25: Perspective view of suitcase with full-length staggered wheel arrangement.

The following disclosure describes the invention in connection with one preferred embodiment, the suitcase.

Furthermore, one should understand that the drawings are not to scale and those graphic symbols, diagrammatic representatives, and fragmentary views, in part, illustrate the embodiment. In certain instances, the disclosure may not include details related to the embodiment itself which are not necessary for an understanding of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference now to FIG. 1, there is illustrated an article of luggage, suitcase 21, constructed in accordance with one of the preferred embodiment of the invention. The suitcase 21 is made up of traditional parts; housing, main body wheels 22 and telescopic tube assembly 23. Also shown in FIG. 1 is the invention apparatus, staggered wheel mechanism 24 and latch mechanism 25.

The suitcase 21 includes generally parallel, spaced apart front and back panel 41 and 42 respectively. The panels 41 and 42 are connected about their periphery by a wall member 43. The wall member 43 extends between panels 41 and 42 thereby defining the volume of the suitcase. The wall member 43 has a top portion 44, a bottom portion 45 and side portions 46 and 47.

The front panel 41 and the wall member 43 are preferably made of soft, flexible material, such as fabric. A zipper or any other means may be provided on the periphery of the front panel 41 for opening and closing the suitcase 21. The panels 41, 42 and wall member 43 materials, suitable openings into the suitcase, the telescopic tube assembly 23, main body wheels 22 and placement of handles to carry the suitcase are well known to those skilled in the art.

For this invention the back panel 42 and bottom portion 45 is made of a suitable rigid, lightweight plastic material, typically used in suitcase construction, to mount the staggered wheel mechanism 24, the latch mechanism 25 and the telescopic tube assembly 23.

Additionally the back panel 42 should be so constructed that it has appropriate recesses 48A & 48B to accommodate the staggered wheel mechanism 24 the latch mechanism 25 the telescopic tube assembly 23 and the main body wheels 22 as shown in FIG. 4. The depth of the recesses should be appropriate so that the staggered wheel mechanism 24 sits flush in the recess when in a retracted position as is shown in the FIG. 3.

The back panel 42 also has a built in bracket 49 to pivotally mount the top end of the staggered wheel mechanism 24. Alternately a suitable bracket could be separately affixed to the rear panel 42 for the same purpose. Another alternative would be to do away with the bracket 49 altogether and pivotally mount the top end of the staggered wheel mechanism onto the telescopic tubes 23 similar to what is shown in FIG. 24 of the shopping basket, using clamps 149 and extended pivot shaft 150

As shown in FIG. 5 the telescopic handle assembly 23 comprises of the outer base tubes 51, the inner telescopic tube 52 and the handle 53. The outer base tubes 51 telescopically receive the inner telescopic tubes 52 when the handle 53 is retracted. The telescopic handle assembly 23 may have a button 54 on the handle 53 to operate well known interlocking mechanism of the telescopic tubes. The outer base tube 51 of the telescopic handle assembly 23 is mounted in the recess 48A of the back panel 42 and is firmly held in place by the upper bracket 55 and the bottom bracket 56. The upper bracket 55 is mounted in the handle recess 48B, shown in FIG. 3, and parallel to the top portion 44 of the wall member 43. The placement of the upper bracket 55 and its relation vis-á-vis the telescopic tubes are shown in FIGS. 1, 3 & 5. The upper bracket 55 is suitably secured to the rigid rear panel 42 by means of screws or rivets. The lower end of the outer base tube 51 is placed in the base caps 57, which are part of the lower bracket 56, and secured by means of diagonal screws. The lower bracket 56 is mounted on the bottom portion 45 of the wall member 43 by means of rivet or screws. The bottom portion 45 should be suitably shaped for the recesses 48A and the lower bracket 56. The lower bracket 56 could also be made as an integral part of the bottom portion 45. The interlocking, retraction and extension mechanism of the telescopic handle assembly 23 and the corresponding mounting is well known to those skilled in the art. For the purposes of this invention the telescopic handle assembly 23 tubes should be so spaced so as to accommodate the staggered wheel mechanism 24 as shown in FIGS. 1 & 3.

Suitcase 21 also includes a pair of wheels 22 found in a traditional wheeled luggage. The wheels 22 are preferably positioned at the corner junction of back panel 42 and the bottom portion 45 of wall member 43. As in traditional wheeled luggage the wheels 22 will primarily be used when moving the suitcase 21 over a planar surface. The wheels 22 along with legs (not shown) suitably positioned on the bottom portion 45 support the weight of the suitcase 21 when in the upright, or at-rest, position.

As shown in FIG. 1 suitcase 21 further includes the staggered wheel mechanism 24 and the latch mechanism 25. The staggered wheel mechanism 24 is pivotally connected to both the back panel bracket 49 and the lower bracket 56 to allow movement between the retracted position FIG. 3 and fully deployed position as shown in FIG. 1. Intermediate position is shown in FIG. 6.

As shown in FIG. 6, 8 and FIG. 11 the staggered wheel mechanism 24 comprises of wheel apparatus 58 and the link apparatus 59. FIGS. 9 through 15 show the different views, partial, perspective, exploded, of the staggered wheel mechanism 24. As shown in FIGS. 11, 14 and 15 the wheel apparatus 58 in turn consists of two spaced apart wheel assemblies 60, the cross-member 61 and a threaded/non-threaded bolt 62.

As shown in FIG. 14 the wheel assembly 60 in turn comprises of wheel frame 63, in-line wheels 64 with corresponding axles 65 and cover strip 66. The wheel frame 63 structure is such that it has two channels 63A and 63B running along its length. The wheel frame 63 is preferably fabricated as one single unit with a oval shaped head that has suitable orifices 69 through which the cross-member 61 and the bolt screw 62 can engage. The elongated portion of the oval shaped head is along the length of the wheel frame 63. The lower end of wheel frame 63 is connected to hinges 77 which in turn are fixed to the lower bracket 56. The in-line wheels 64 are laid out in an array in each channel 63A & 63B of the wheel frame 63. For clarity the in-line wheels 64 laid out in channel 63A is designated as wheel array 64A and in-line wheels 64 laid out in channel 63B are designated as wheel array 64B. The wheel arrays 64A and 64B are rotatably mounted in their respective channels 63A and 63B using axles 65. As is shown in FIGS. 9, 10 and 15 the height of the outer walls 63D of the channels 63A and 63B should be, when measured from inside the channel, at least 2 mm more than the radius of the wheels to allow free rotation. The midrib, 63C, of the wheel frame 63 should be, again measured from inside the channel, no more than ¾ of the diameter of the in-line wheels 64. To mount the axles 65, cylindrical grooves 67 are made on either side of the midrib 63C. The grooves through the midrib 63C can be up to ¾ of its thickness. Also semi-cylindrical grooves 68 are made into the outside walls 63D of the wheel frame for the second end of the axles 65. Complementing semi-cylindrical grooves are made into the cover strip 66. The length of the grooves on the outside wall 63D and in the cover strip should not be more than half their respective widths. The cover strip 66 is fixed on the outside walls 63D of the channel 63A and 63B by means of screws to secure the axles.

The axles 65 are spaced equidistant from each other. The distance between any two adjacent axles 65, from its centre, should be slightly more than the diameter of the wheel 64. This is so that the edges of the adjacent in-line wheels 64 in wheel arrays 64A & 64B have got at least a 1 mm of clearance to freely rotate on its axle 65. The distance between the edges of the adjacent in-line wheels 64 should kept below 5 mm for smoother movement over the stairs.

The in-line wheels 64 used in forming the two wheel arrays 64A & 64B are of the same diameter and its axles 65 too are also equally spaced apart. However the wheel arrays 64A and 64B are mounted in a staggered fashion in their respective channels 63A & 63B, as shown in all figures showing staggered wheel mechanism 24. With this arrangement if wheel array 64A is laterally moved into channel 63B, the centers of wheels in wheel array 64A would fall right in between edges of two wheels of wheel array 64B and vice-versa.

The staggered wheel arrangement creates a near linear, continuous rotary edge at the outer edge of the wheels as shown in side views, FIGS. 2 and 8. This in turn eliminates the drawbacks of the prior art and leads to easy movement of the wheeled luggage over stairs.

Further the wheel frame 63 fabrication could be such that the upper ¼ths of its length is slightly tilted outwards for better engagement of the staggered wheel mechanism 24 with the steps whilst ascending. However the wheel frame 63 fabrication could be fabricated without the tilt.

The two wheel assemblies 60 are joined together at the top end by the cross member 61 and secured using a threaded/non-threaded bolt 62. Orifices 69 are made at the top end in the wheel frame 63 as shown in FIG. 14 and FIG. 15 to interconnect the circular cross-member 61 and the bolt 62 through the wheel frame 63. To prevent the bolt 62 from getting unscrewed by use over time, due to constant deployment and retraction of staggered wheel mechanism, bolt 62 can be further secured to the cross member 61 by a diagonal screw engaging the cross-member 61 and bolt 62 through the respective orifices 61A and 62A. The screw should sit flush within the cross-member 61 orifice 61A so as to not to impede the link apparatus. To permit assembly a hole or a slot could be made into the eye portion 78 of the lower link 71.

As shown in FIGS. 11-13, the link apparatus 59 consists of upper link 70 and the lower link 71. The hinge 72 pivotally connects the lower link 70 to the upper link 71. The torsion spring 74 mounted in the pivot pin 73 of the hinge 72 enables automatic deployment of the wheel apparatus 58 when the catch 84 in the latch mechanism 25 is raised. The staggered wheel mechanism 24 when stowed away is held in the retractable position by the latching mechanism 25.

The upper end of the upper link 70 is pivotally connected to the back panel 42 by a suitable pivot mechanism. In this case a bracket 49, which could be part of single mould of back panel 42, is used to pivotally connect the pivot pin 75 as shown in FIG. 11 and FIG. 12. The pivot pin 75 is held in position by a suitable clip 75A slipped over the groove 76 at either end of the pivot pin 75 from inside the suitcase cavity.

The lower link 71 is pivotally connected to the cross-member 61 by the eye portion 78. The cross-member 61 acts as a pivot shaft to the lower link 71. When the staggered wheel mechanism 24 is fully deployed the two links 70 and 71 will line up and lock in place when in use. To firmly prevent the link apparatus from folding when in use, a simple locking mechanism such as a sliding pin or link plate, on the side of the upper link engaging with the lower link when deployed, could be used. However any suitable, well known, locking mechanisms could be used as part of the link apparatus 59.

The lower end of the both the wheel assemblies 60 is pivotally connected to the lower bracket 56 by a suitable pivot mechanism e.g. a bracket with pivot pin or in this case, as shown in the FIG. 11 by hinges 77. The lower bracket 56 is rigidly fixed to the bottom portion 45. Alternately the hinges could be directly fixed to the rigid bottom panel 45.

The lower bracket 56 and thereby the staggered wheel mechanism 24 should be so mounted that the outer edge of the in-line wheels 64 and the outer edge of the main body wheels 22 align when staggered wheel mechanism 24 is fully deployed as shown in FIG. 17. This arrangement is needed to ensure that the main body wheels 22 of the suitcase 21 do not add a bump to the suitcase movement over the stairs. This arrangement also adds to the overall length of the available wheel apparatus 58.

FIG. 16 shows an alternative linkage between the lower link 71 and the cross-member 61. In the figure the cross-member 61 is rigidly fixed to the back of the wheel frame 63 instead of the top as in earlier figures. A pillow block 79 like structure, which acts as a bracket, is affixed on the back of the wheel frame 63 to hold the cross-member 61 by means of a screw. The pillow block bracket 79 may be separately affixed or fabricated as part of the wheel frame 63. Another major change is that channels 63A and 63B, of both the wheel assemblies 60, are left open at the top. One wheel, of either wheel arrays 64A or 64B of each wheel assembly 60, depending on the construction, is allowed to protrude out of the channel along its length. This arrangement will be helpful in situation where the wheel apparatus 58 happens to be of shorter length than the distance between two steps edge, creating a possibility of the wheel apparatus 58 getting stuck in the steps.

The overall dimensions of the staggered wheel mechanism, wheel frame 63, width of the channels 63A & 63B, thickness of the channel walls and back portion, dimensions of axle 65 and in-line wheels 64 will all depend on the shape and size of the embodiment, weight carrying capacity of the embodiment and the materials chosen for the staggered wheel mechanism. Depending on the material chosen for the wheels 64, preferably polyurethane, the dimensions of wheels 64 and axles 65 should be such that it should be able to bear the anticipated weight of a fully loaded embodiment. Polyurethane properties like elasticity of rubber combined with the toughness and durability of metal makes it suitable to keep the wheel dimensions and overall weight of the staggered wheel mechanism 24 to the minimum. This is turn will not effect the payload capacity and preserve the overall aesthetics of the embodiment. The wheels 64 may be knurled for better gripping.

The length of the wheel apparatus 58 will also depend more on the average distance between two steps edge and less on the shape and size of the embodiment. The overall length of the wheel apparatus 58 along with wheels 22 should be at least the average distance between edges of two steps so that the top edge of the wheel apparatus does not get caught in the stairs. However for embodiments that do not have sufficient height the staggered wheel mechanism shown in FIG. 16 is more suitable. This is so because it has wheels 64 at the top end of the wheel apparatus which will continue with the rolling motion even when it would look like possibly getting caught in the higher step.

It is also of importance to discuss the appropriate length of the link apparatus 59 which in turn determines the deployed rotational angle of wheel apparatus 58. As per some documents about research there are various configurations of stair steps having different depth and height, and different ratios of the former to the latter, according to conditions of location. The same documents mention that by experiment a baggage cart having an overall length of 90 cm tends to have an inclination of 38 or so with respect to a person 165 cm tall who is drawing the cart by hand on a flat place, 35 or so with respect to a person 180 cm tall, and 43 with respect to a person 150 cm tall. Thus, in almost all cases, the inclination of a baggage cart with respect to a person who is drawing it is within a range of 35 to 43 degrees. However when the suitcase 21 is taken over stairs the desired angle will be dependent on the dimension of the steps, steepness etc. and the document mentions that the angle may vary between 27 to 35 degrees. So the overall length of the link apparatus 59 should be so that the angle formed by the wheel apparatus 58 is around 30 degrees to the wall of the rear panel 42 for easy comfortable pull over the stairs. This is just a suggested angle and it could vary.

The preferred method of stopping on stairs whilst using the staggered wheel mechanism 24, for this particular embodiment, i.e. suitcase 21, is to straighten out the suitcase 21 in the upright position on the steps whilst ascending or descending the stairs.

FIGS. 18, 19 & 20 illustrate a preferred embodiment of the latch mechanism 25 and are well known. The slider latch mechanism 25 comprises of the housing 80 with slider guides 82 and posts 81. The slider guides 82 engage with vertical flanges 85 on the catch structure 83 and limit it to an up/down vertical movement. The two vertical posts 81 on the housing 80 slidably engage with first, the orifices 87 on the horizontal flange 86 of the catch structure 83 and than with the spring 88. The spring 88 is held in place by the housing cover 89 which is fixed to the housing by means of screws. In the default position the catch 84 on the catch structure 83 is pushed down by the spring 88 in its relaxed state. The catch 84 in turn engages with the groove 90 on the eye portion 78 of the lower link 71 when the staggered wheel mechanism 24 is in fully retracted position. The luggage handler will have to push the catch 84 up against the force of the spring 88 to disengage it from the groove 90 and deploy the staggered wheel mechanism 24. To latch in the retracted position the catch 84 will have to be raised or the wheel apparatus will have to be pushed against the latch which in turn will raise the catch 84 portion of the latch mechanism 25.

FIGS. 21, 22 and 23 illustrate a pivotal latch mechanism. The previous slider latch mechanism 25 illustrated in FIGS. 18, 19 and 20 would require the luggage handler to bend down to disengage the latch and deploy the staggered wheel mechanism. The pivotal latch mechanism attempts to provide a better deployment mechanism wherein the user will not have to bend all the way down. It provides a button 91 that goes through the orifice 92 and engages with the link rod 93. The link rod 93 has a fork 93A at the lower end which engages with the crossbar 94 to form a fork joint. The crossbar 94 rests on rear end of the lever 98 and is kept in position on the lever by projection 97. Additionally the crossbar 94 is kept in position by suitable cavities in the back panel 42. Projection 97 can be also suitably modified into a loop structure to hold the crossbar 94 in place. The front end of the lever 98 has a projection 99 which acts as a catch and engages with the grooves 96 on the wheel frame 63 because of the force exerted by the torsion spring 101. The lever mechanism 95 is rigidly fixed to the rear panel 42 by using clamps 102 holding the fulcrum pin 100 on either side. In the default position the projection 99 is held down by the spring force wherein the button 91 is in the raised state. When the button 91 is pushed the staggered wheel mechanism 24 will get deployed as the rear end of the lever 98 will get pushed down thus raising the catch 99. The button 91 will have to be pushed down momentarily to stow away the staggered wheel mechanism 24 and latch it.

FIG. 24 shows the staggered wheel mechanism 24 on a shopping basket. Since there is no rigid rear panel the pivot pin 150 is appropriately scaled to pivotally engage with the clamps 150 on the tubes.

In FIG. 25 the staggered wheel arrangement is mounted along the full length of the rear panel of the suitcase. In this instance the telescopic handle assembly will have to be made pivotable at the junction of the top portion and the back panel of the suitcase. The back panel recesses will have to be suitably modified to accommodate the full length of staggered wheel.

The present invention, staggered wheel mechanism, could be suitably exploited for other embodiments. 

1. A suitcase comprising of a rigid telescoping pull handle and a set of spaced apart wheels, between the back panel and bottom wall of the suitcase housing, permits movement over a planar surface and a staggered wheel mechanism, pivotally mounted on the back panel of the suitcase, for movement of the suitcase over a flight of stairs.
 2. A suitcase as defined in claim 1, has recesses in the back panel of the suitcase, so that the staggered wheel mechanism sits flush when stowed away.
 3. A suitcase as defined in claim 1, wherein the staggered wheel mechanism comprises of a pivotally connected wheel apparatus and a link apparatus.
 4. A suitcase as defined in claim 3, wherein the staggered wheel mechanism itself is pivotally connected to the back panel by lower free end of the wheel apparatus and the top free end of the link apparatus.
 5. A suitcase as defined in claim 3, wherein the wheel apparatus comprises of two spaced apart parallel wheel assemblies, with the spacing proportional to at least ¼ Of the breadth of the suitcase back panel.
 6. A suitcase as defined in claim 5, wherein each wheel assembly is made up of wheel frame and in-line wheel arrays with their corresponding axles.
 7. A suitcase as defined in claim 6, wherein the wheel frame, has two parallel channels, each at least 12″ in length, to receive in turn one in-line wheel array each with their corresponding axles to form two wheel columns.
 8. A suitcase as defined in claim 7, wherein the axles of the wheels, that make up the wheel array, are parallel to each other and are so spaced apart in the channel that the distance between outer edge of any two adjacent wheels, at their nearest point, is at least 1 mm and preferably not more than 5 mm.
 9. A suitcase as defined in claim 7, wherein the axles of the wheels are securely held in place in the wheel frame channel walls so as to allow free rotation of their respective wheels.
 10. A suitcase as defined in claim 7, wherein the in-line wheel array in each channel is arranged in a staggered fashion, such that if a line is traced from the center of the wheels in one channel it would exactly fall in between the gap of two adjacent wheels in the second channel and vice-versa.
 11. A suitcase as defined in claim 10, wherein the wheels of the wheel array when placed in the channel ¾ of the diameter of the wheels is in the channel and ¼ Of the diameter of the wheels protrude exterior to the channel, when measured vertically with respect to the channel walls.
 12. A suitcase as defined in claim 11, the staggered arrangement of wheels offers an almost linear, continuous rotary outer surface to the edge of the steps.
 13. A suitcase as defined in claim 10, wherein the in-line wheels since placed in a staggered fashion the topmost wheel in one of wheel arrays, could be either fully contained within the channel or could be left protruding out of the channel by at least ¼ of the wheel diameter along the channels length in addition to the ¼ Of the diameter along the channels walls.
 14. A suitcase as defined in claim 5, the two wheel assemblies are mirror images of each other such that when the staggered wheel mechanism is mounted on the suitcase, a wheel each, from the two spaced apart wheel assemblies, equidistant from the bottom edge of the back panel of the suitcase, are in concurrent contact with a given steps edge.
 15. A suitcase as defined in claim 3, wherein the link apparatus comprises of two links that are hinged together along with a torsion spring to facilitate deployment and stowing away of staggered wheel mechanism.
 16. A suitcase as defined in claim 15, the length of the link apparatus is such that the angle between the back panel of the suitcase and the wheel apparatus forms an angle of at least 30°.
 17. A suitcase as defined in claim 1, has a locking mechanism to hold the staggered wheel mechanism when stowed away in the recess of back panel of the suitcase.
 18. The staggered wheel mechanism could be suitably mounted on a shopping basket to facilitate its movement on a flight of stairs. 